public static bool TryQueryStructure(
Structure term,
PrologContext context,
out ELNode foundNode,
out ELNodeEnumerator enumerator)
{
//
// Dispatch based on the functor and arity.
//
// Handle root queries, i.e. /Key
if (term.IsFunctor(Symbol.Slash, 1))
return TryRootQuery(term, context, out foundNode, out enumerator);
if (!IsELTerm(term))
throw new Exception("Malformed EL query: " + ISOPrologWriter.WriteToString(term));
if (term.IsFunctor(SBindNodeOperator, 2))
{
var variableToBind = term.Argument(1) as LogicVariable;
if (variableToBind == null)
throw new ArgumentException("RHS of >> must be an uninstantiated variable: "+ ISOPrologWriter.WriteToString(term.Argument(1)));
foundNode = null;
return TryNodeBindingQuery(out enumerator, term.Argument(0), variableToBind, context);
}
return TryChildQuery(
out foundNode,
out enumerator,
term.Argument(0),
term.Argument(1),
term.Functor == Symbol.Colon,
context);
}
internal IEnumerable<CutState> Retract(object term)
{
Structure head = Term.Structurify(term, "Argument to retract must be a valid term.");
object body = Symbol.True;
if (head.IsFunctor(Symbol.Implication, 2))
{
body = head.Argument(1);
head = Term.Structurify(head.Argument(0), "Invalid clause head.");
}
return Retract(head, body);
}
internal static void WriteAndPossiblyParenthesize(StringBuilder s, object o)
{
Structure t = o as Structure;
if (t != null && t.IsFunctor(Symbol.Comma, 2))
{
s.Append('(');
Write(s, o);
s.Append(')');
}
else
{
Write(s, o);
}
}
private void WritePrologList(StringBuilder s)
{
s.Append('[');
bool first = true;
object current = Canonicalize(this);
LogicVariable l = current as LogicVariable;
if (l != null && l.IsBound)
{
current = l.Value;
}
while (current != null)
{
Structure t = current as Structure;
if (first)
{
first = false;
}
else if (t == null)
{
s.Append(" | ");
}
else
{
s.Append(", ");
}
if (t == null)
{
Write(s, current);
current = null;
}
else
{
if (t.IsFunctor(Symbol.PrologListConstructor, 2))
{
Write(s, t.Argument(0));
current = t.Argument(1);
}
else
{
WriteAndPossiblyParenthesize(s, current);
current = null;
}
}
}
s.Append(']');
}
/// <summary>
/// Returns the Term whose functor is the first element of the list and whose arguments are the other elements of the list.
/// Functional version of =..
/// </summary>
public static Structure FromList(Structure listExpression)
{
if (listExpression == null || !listExpression.IsFunctor(Symbol.PrologListConstructor, 2))
{
throw new ArgumentException("Argument must be a prolog list");
}
object functorArg = listExpression.Argument(0);
if (functorArg == null)
{
throw new ArgumentException("First element of list (functor) must be a symbol.");
}
var functor = functorArg as Symbol;
if (functor == null)
{
throw new ArgumentException("First element of list (functor) must be a symbol.");
}
return(new Structure(functor, Prolog.PrologListToArray(listExpression.Arguments[1])));
}
/// <summary>
/// Creates a KnowledgedBaseRule given a Term object for a :- expression.
/// </summary>
public static KnowledgeBaseRule FromTerm(Structure structure, bool checkSingletons, string source, int line)
{
if (structure == null)
{
throw new ArgumentNullException("structure");
}
if (structure.IsFunctor(Symbol.Implication, 2))
{
var body = new List <Structure>();
UnwindCommaExpression(structure.Argument(1), body);
if (structure.Argument(0) == null)
{
throw new ArgumentException("head of rule is null");
}
Structure head = Term.Structurify(structure.Argument(0), "Head of :- must be a valid proposition or predicate.");
if (head == null)
{
throw new ArgumentException("Head of rule is not a term.");
}
return(MakeRule(head, body, checkSingletons, source, line));
}
return(MakeRule(structure, null, checkSingletons, source, line));
}
/// <summary>
/// Add a term (fact or rule) to the KB.
/// </summary>
public void Assert(Structure structure, bool atEnd, bool checkSingletons)
{
if (structure == null)
{
throw new ArgumentNullException("structure", "Term to add to KB may not be null.");
}
//structure = structure.Expand();
if (structure == null)
{
throw new ArgumentNullException("structure");
}
Structure head = structure.IsFunctor(Symbol.Implication, 2)
? Term.Structurify(structure.Argument(0),
"Head of :- must be a valid proposition or predicate.")
: structure;
if (head.IsFunctor(Symbol.ColonColon, 2))
{
var argument = head.Argument(0);
var kb = argument as KnowledgeBase;
if (kb == null)
{
var o = argument as GameObject;
if (o != null)
{
kb = o.KnowledgeBase();
}
else
{
var c = argument as Component;
if (c != null)
{
kb = c.KnowledgeBase();
}
else
{
throw new ArgumentTypeException(
"assert",
"knowledgebase",
argument,
typeof(KnowledgeBase));
}
}
}
if (structure.IsFunctor(Symbol.Implication, 2))
{
kb.Assert(
new Structure(Symbol.Implication, head.Argument(1), structure.Argument(1)),
atEnd,
checkSingletons);
}
else
{
kb.Assert(structure.Argument(1), atEnd, checkSingletons);
}
}
else
{
if (PrologPrimitives.Implementations.ContainsKey(head.Functor))
{
throw new PrologException(
new Structure(
"error",
new Structure(
"permission_error",
Symbol.Intern("modify"),
Symbol.Intern("static_procedure"),
Term.PredicateIndicatorExpression(head))));
}
KnowledgeBaseRule assertion = KnowledgeBaseRule.FromTerm(
structure,
checkSingletons,
Prolog.CurrentSourceFile,
Prolog.CurrentSourceLineNumber);
PredicateInfo info = EntryForStoring(head.PredicateIndicator);
PredicateInfo parentInfo;
if (!info.Shadow && this.Parent != null &&
(parentInfo = this.Parent.CheckForPredicateInfoInThisKB(head.PredicateIndicator)) != null &&
!parentInfo.External)
{
throw new PrologException(
new Structure(
"error",
new Structure(
"permission_error",
Symbol.Intern("shadow"),
Term.PredicateIndicatorExpression(head))));
}
info.Assert(assertion, atEnd);
}
}